Railroad bridges are frequently erected over waterways trafficked by pleasure boats, merchant ships or military vessels. The superstructures or equipment carried by the superstructures of these craft are sometimes quite high with respect to the water surface and may extend above the elevation of a railroad bridge deck. Several types of railroad bridges have movable decks to permit passage of tall vessels as the need arises. Although their methods of operation may vary, such bridges possess at least one characteristic in common. That is, at least a portion of the bridge deck may be selectively disposed into a first position for permitting passage of rolling stock thereover and a second position for permitting passage of watercraft by or under the deck. Included among these classes of bridges are the vertical lift bridge, the bascule bridge and the swing bridge. A vertical lift bridge normally includes a pair of towers disposed on opposite ends of a bridge deck which include machinery for raising and lowering the deck while maintaining the deck in substantially horizontal orientation. A bascule bridge typically includes a bridge deck pivotally connected about a horizontal pivot axis to a bridge approach, pier, or the like, such that the deck may swing upwardly and downwardly. In a swing bridge, the deck is generally supported atop a turntable and rotates approximately 90.degree. in a substantially horizontal plane between rail passage and watercraft passage positions.
Steel rail or track is subject to thermal expansion and contraction. Accordingly, a certain gap must be maintained between the ends of rails or tracks carried by a movable bridge deck and the ends of adjacent rails or track. Depending on the atmospheric temperature range to which the bridge is likely to be exposed and the length of rails involved, the required gap may range from about one to three inches or more. However, traverse of gaps of this magnitude by the wheels of rolling stock is not recommended because of the potential for wheel and/or track damage and possible derailment of the rolling stock.
Miter or rider rails are transition rails used to bridge the gap between adjacent ends of a section of vertically movable track and a section of stationary track known as the "running rails". CMI-Promex, Inc. of Pedricktown, N.J. manufactures a miter rail system including a rider rail approximately three feet in length which is bolted to an end of the stationary rail and spans the distance between the ends of the stationary and movable rails. The rider rail has a convex upper surface of constant radius whereby the upper surface of the rider rail is slightly lower than the running rails at its ends and slightly higher than the running rails at its center.
As the wheels of rolling stock travel over a running rail and encounter the rider rail they become supported by the rider rail and slightly lifted with respect to the upper surfaces of the running rails. Upon passing the rider rail, the wheels come into contact with the upper surface of the running rail at the downstream side of the track joint.
As is known, rolling stock wheels have two rail contacting surfaces, the "flat" and the "flange". The flat contacts the upper surface of the head portion of rail or track. the flange extends substantially perpendicular to the flat and contacts the substantially vertical inner face of the head portion of the rail. The flat bears the majority of the weight of the rolling stock and the flange functions to keep the wheels in engagement with the track. To enhance reliable contact between the rolling stock wheels with the underlying track, the opposed rails of the track are usually installed slightly off vertical. More particularly, each of the rails is canted or tilted slightly inwardly toward the other at approximately 1.5.degree. from vertical.
The upper end edges or corners of the rider rails of miter rail systems such as the aforementioned CMI-Promex, Inc. system frequently become chipped off during use. The chipped areas, in turn, promote the generation and promulgation of cracks that reduce the structural integrity of the rider rails. Although the chipping damages is believed to be caused by contact with rolling stock wheels, the manner by which the rider rail ends become damaged is not fully understood, especially since the upper surfaces of the rider rails at the end regions thereof are lower in elevation than the adjacent running rails.
An advantage exists, therefore, for a miter rail system including a rider rail which is resistant to damage resulting from contact with rolling stock wheels.